The trolleybus as an electrically powered transit mode running on streets has several interesting features, but it has never reached the top ranks among service choices. It is a cross between a bus and a streetcar, and not necessarily only the best characteristics of those two are to be found in the resulting vehicle. It looks and acts almost like a bus, except that it is tied to an overhead network of wires for power supply; it operates somewhat like a streetcar, but the reach of the power pickup poles allows it to move across several lanes.

In 1998, there were 880 active trolleybus vehicles operating in the United States, accommodating 182 million passenger miles that year. The number of vehicles represents 0.7 percent of the national transit fleet, the passenger miles only 0.4 percent of the total. The corresponding figures in 1984 (an interim peak) were 664 vehicles and 364 million passenger miles. (The all-time peak for trolleybuses in the United States were the years 1949 and 1950, with ridership dropping steeply during the following decade.)

The trolleybus has service capabilities that are almost identical to those of a regular diesel bus, and therefore only those elements that are different will be described and discussed in this chapter.